Improving the cultivation and detection of susceptibility to antibacterial drugs in cultures of Mycobacterium avium subsp. paratuberculosis

A dense nutrient medium for cultivating the paratuberculosis pathogen has been developed with ingredients of natural origin – extracts from birch wood ash and peat oxidate. The possibility of its use for phenotypic detection of the sensitivity of paratuberculosis mycobacteria to antibacterial drugs has beenstudied. The Lowenstein-Jensen commercial nutrient medium with mycobactin served as an analogue for the preparation of the experimental medium. Analysis of the composition of the extract from birch wood ash and peat oxidate showed the presence of microand macroelements necessary for the vital activity of mycobacteria. When seeding biomaterial from cattle with pathological changes characteristic of paratuberculosis, three mycobacteria cultures were isolated on the experimental and commercial Lowenstein-Jensen nutrient medium with mycobactin. The growth rate of the cultures on the experimental medium was +(1), while on the commercial medium it was +/–(0). Based on microbiological studies, the obtained isolates were classified as M. paratuberculosis. When cultivating suspensions of the standardized strain of M. paratuberculosis and the isolated field isolates, the appearance of primary colony growth on the experimental nutrient medium was noted 3±0.42 days faster than on the commercial one, and intensive growth was noted 7±0.30 days faster. When seeding the biomaterial, the primary growth of mycobacteria identified as M. paratuberculosis on the experimental medium was noted on average 7±0.1 days faster than on the commercial medium, and intensive growth was 3±0.62 days faster. Phenotypic determination of the sensitivity of the standardized strain and field isolates to 11 antibacterial drugs using the disk diffusion method revealed their susceptibility to all antibiotics used and showed the absence of statistically significant differences between the zones of growth inhibition on commercial and experimental nutrient media. It has been established that the experimental nutrient medium has diagnostic efficiency and information content with the possibility of using it for phenotypic detection of the sensitivity of paratuberculosis mycobacteria cultures to antibacterial drugs, while it is cheaper and easier to prepare

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